BOSTON – Officials overseeing the investigation into this week’s catastrophic water main breach are sifting through engineering records and contract documents to try to find out if there are other potentially faulty couplings in the system.

The failure of a massive metal coupling is being blamed for Saturday’s breach that sent water pouring into the Charles River, forcing Gov. Deval Patrick to issue a boil water order for about 2 million eastern Massachusetts residents.

The order was lifted Tuesday.

Investigators believe the one-ton coupling, which held together sections of a 10-foot water pipe, gave way, prompting the emergency.

On Wednesday, searchers were set to resume looking for the coupling, believed buried under some of the 400 cubic yards of soil and sand blown into the river by the breach.

Ria Convery, spokeswoman for the Massachusetts Water Resources Authority, which oversees water and sewer operations in much of the greater Boston area, said the search had to be postponed until Thursday to give Weston conservation officials time to survey the area for damage from the blowout.

“The work will start in earnest (Thursday),” she said.

Barletta Heavy Division Inc., the Canton, Mass.-based company that built the pipe, is expected to excavate two large sand bars that were formed when the pipe blew.

The coupling is believed buried under one of the sand bars.

The governor said an investigation is needed to find out exactly what caused the coupling to give way and to ensure the problem isn’t repeated.

Patrick said he wanted to determine if there were any other problematic couplings in the system.

He also said the 30 cities and towns placed under the boil water order narrowly avoided a much bigger problem.

“Fortunately, the pipe itself did not rupture,” he said during his monthly radio show on WTKK-FM.

“Had that been the case, we would be weeks with this boil water order.”

The MWRA board of directors is planning a special meeting Thursday afternoon to review the break. The board is to consider whether to appoint a commission to investigate the breach.

Democratic House Speaker Robert DeLeo said again Wednesday that he will schedule a public hearing on the breach to determine what happened and to make sure that the cost of the accident isn’t passed on to MWRA customers.

Patrick said he didn’t think any agency had any intention of passing on the costs.

Patrick also said that he is asking the water authority to consider accelerating work on a second water delivery system that could act as a backup in the case of another breakdown in the existing pipe.

Having a second system would avoid any repeat of the recent disruption in the delivery of clean drinking water, he said.

The federal government is also pitching in to help cover some of the costs.